Cold‐evoked potentials versus contact heat‐evoked potentials—Methodological considerations and clinical application

Abstract

Background Previous studies investigated cold‐evoked potentials (CEPs) for the assessment of the integrity of cold‐mediating A‐delta fibres and the spinothalamic tract. Nevertheless, several methodological questions remained unanswered to proceed to clinical application. How do latencies and amplitudes vary between CEPs and contact heat‐evoked potentials (CHEPs)? Are there differences between variable and fixed thermode positions or between glabrous and hairy skin? Are CEPs recordable in patients with abnormal cold processing? Methods A total of 16 healthy subjects were tested with CEPs and CHEPs at the face, hand and foot. Variable and fixed thermode positions, hairy and glabrous skin were compared. Three patients with abnormal cold processing were tested with CEPs and quantitative sensory testing. Results Compared to CEPs, CHEPs latencies were significantly longer at all locations, amplitudes were significantly larger at the face and the hand whilst comparable at the foot. CEPs and CHEPs did not differ significantly between variable and fixed thermode positions using inter stimulus intervals of 8–12 s. CEP latencies were increased by around 20% at the glabrous skin. Patients with known abnormal cold processing (central pain, polyneuropathy, Fabry's disease) showed increased N2 latencies as compared to normal controls. Conclusions Inter stimulus intervals of 8‐12 s allow the use of a fixed thermode position for reliable CEPs/CHEPs recording. Hairy skin stimulation results in faster latencies as compared to glabrous skin, without influencing EP amplitudes. In patients with abnormal cold processing, CEPs are recordable and increased latencies may be expected as compared to healthy controls and the healthy contralateral side. Significance Cold‐evoked potentials are an innovative, non‐invasive technique to assess cold detection and processing objectively. This study shows that CEP can be recorded from the hairy and glabrous skin, regardless of using fixed or variable thermode positions. Loss of A‐delta fibre function leads to an increased CEP latency, consistent with loss of cold detection in the QST.

Conduction velocity of the cold spinal pathway in healthy humans

“…Our study investigating cold spinal pathway conduction velocity supports the view that cold‐evoked potentials may be an alternative to laser‐evoked potentials recording to assess the spinothalamic tract in humans (De Keyser, 2018; Hüllemann, 2019). Admittedly, cold stimulation evokes lower amplitude and less reproducible vertex potentials than noxious laser stimulation (De Keyser, 2018; Hüllemann, 2016; Leone, 2019).…”

EEG-based sensory testing reveals altered nociceptive processing in elite endurance athletes

“…Subjective pain testing is the gold standard in research, e.g., via questionnaires such as the McGill pain questionnaire (Main 2016), via quantitative sensory testing (QST) (Rolke et al 2006), or with paradigms testing the conditioned pain modulation (CPM) (Nir and Yarnitsky 2015). In addition, electroencephalography (EEG)-based cortical-evoked potentials in response to noxious stimuli have been introduced as promising tools (van den Broeke et al 2015;Özgül et al 2017;Hüllemann et al 2019;Fabig et al 2021). Nociceptive testing using EEG can be carried out in a non-verbal population such as newborn infants (Hartley et al 2017) or in animals (Murrell and Johnson 2006), and advances in computerized analytics of the EEG, like the analysis of the event-related spectral perturbation (ERSP) and the inter-trial coherence (ITC), allow for an in-depth analysis of event-related EEG data.…”

Diagnostik und Therapie neuropathischer Schmerzen

“…In spezialisierten Zentren werden weitere Methoden durchgeführt, um möglichst objektiv Rückschlüsse auf den Status des sensorischen Systems ziehen zu können. Dazu zählen beispielsweise die korneale konfokale Mikroskopie (CCM) und die evozierten Potenziale [18][19][20]. Als "Kann-Empfehlung" haben diese Methoden Einzug in die Leitlinie für die Diagnostik neuropathischer Schmerzen gefunden [4]…”